A conventional apparatus for gasifying pulverized coal comprises a housing provided with a thermal insulation and with an outlet pipe connection for passing off the producer gas and an outlet connection for the discharge of granulated slag. There is a pulverized-coal burner arranged in the upper part of the housing and an overflow pipe for maintaning a water level in the lower part of the housing and a gas-tight tube screen is constricted centrally to divide the interior space of the apparatus into a reaction zone and a radiation zone, and which forms an opening for passing the producer gas and the liquid slag from the reaction zone into the radiation zone. In the reaction zone, this tube screen is fitted with studs carrying a layer of refractory ramming material (USSR patent document No. 1136475, cl. C 10 J 3/08, 1981).
This apparatus has substantial disadvantages:
1. A poor quality of the producer gas is obtained with a high expenditure of energy because the tube screen is constricted centrally, fitted with studs (in the reaction zone) and provided with a layer of refractory ramming material on the studs and also because the apparatus is operated with liquid slag discharge. This means that the producer gas temperature upstream of the central constriction must be higher by 200.degree. to 400.degree. C. than the temperature required for gasification. It is necessary to burn part of the H.sub.2 and CO produced to maintain such a temperature level which, in turn, reduces the quality of the producer gas and increases the oxygen consumption.
2. The apparatus cannot be operated on coals which produce a slag containing constituents having low fusion points, and consequently high vapor pressures, since the radiation zone is provided with a tube screen on which such constituents would deposit and which would be clinkered up gradually as would be the ducts for gas passage; ultimately, this would lead to a failure of the apparatus.
An apparatus for gasifying pulverized coal which is almost similar to the proposed invention with regard to engineering aspect and effects to be achieved comprises a housing with a cover provided with a thermal insulation; an outlet pipe connection for passing off the producer gas, this connection being provided in the side wall of the lower part of the housing; an outlet connection for the discharge of granulated slag being provided axially in the bottom of the housing; a pulverized-coal burner provided axially in the cover of the housing; an overflow pipe for maintaining a water level in the lower part of the housing; a gas-tight tube screen with openings in the top and bottom parts which form tube grids; and inlet pipes for steam injection which are connected to a manifold. This apparatus can be operated in such a way that the gasification process takes place at temperatures ranging above the fusion temperature of the slag. Due to special design features, however, clinkering-up of the tube screen and other surfaces within the apparatus is prevented. These design features contribute to the formation of an areal flow of circulating gas parallel to the tube screen which acts as a protective layer having a temperature below the ash softening point.
This apparatus has substantial disadvantages:
1. A poor quality of the producer gas is obtained with a high expenditure of energy for gas production because the tube screen removes a substantial amount of heat from the producer gas. This removal has to be compensated for by burning part of the product obtained (CO+H.sub.2) to maintain the temperature required for gasification. In this process, the content of CO and H.sub.2 in the producer gas decreases and the oxygen consumption becomes too high.
2. The apparatus cannot be operated on coals which produce an ash containing constituents having low fusion points because such constituents would evaporate and deposit on the tube screen, gradually clinkering it up as well as the ducts between the thermal insulation and the tube screen. This would finally result in in a failure of the apparatus.